Abrasive article and method of making the same



Feb. 5, 1935. G. H. DAVIS ABRASIVE ARTICLE AND METHOD OF MAKING THE SAMEFiled Oct. 1'7, 1951 2 Sheets-Sheet 1 INVENTOR GEORGE H, DAV\5. MW

ATTORNEY Feb. 5, 1935. l G. H. DAVIS 1,989,742

ABRASIVE ARTICLE AND METHOD OF MAKING THE SAME Filed Oct. 17, 1951 2Sheets-Shea?l 2 f2 v( Y I ,f yr )I S INVENTOR GEORGE H. DAV\S.

BY am ,a4/MW ATTORN EY Patented Feb. 5, 1935` UNITED STATES i ABRASIV'EARTICLE AND METHOD 0F MAKING THE SAME George H. Davis, Niagara Falls, N.Y., assigner to The Carbornndnm Company, Niagara Falls, N. Y., acorporation oi' Pennsylvania Application october 17, 1931, serial No.569,441 comms. (c1. 51-278) The present invention relates to flexibleabrasive fabrics, and particularly to a method for increasing the'exibility of such material.

Heretofore, in the manufacture of yflexible abrasive fabrics, it hasbeen proposed to increase the flexibility by passing the material overflexing bars in two directions, at right angles, which process willbreak or crack the abrasive coating in lines which are vmutuallyperpendicular and are diagonal to the fabric. Such method of flexingdoes not wholly i'lex every portion of the fabric but leaves spacesbetween the lines thus exed.

This renders a partial flexibility of the material which tends to reduceor impair its quality.

In accordance with the present invention, the abrasive material isflexed uniformly throughout its entirety or, if desired, only along theedges. By means of balls operating under pressure upon the back of theabrasive fabric, the breaks occur substantially in radial form abouteach particle of grain, leaving no one portion of the fabric untreated.The formation of breaks about the grain particles results in an increasein flexibility of the abrasive-coated fabric and in an article which ismaterially superior to abrasive-coated fabrics exed by previously usedmethods.

vOther advantages of my invention will become apparent from a perusal ofthe drawings forming part of this application, wherein:

Fig. 1 is a diagrammatic side view of the exing apparatus with theabrasive fabric passing therethrough; f Fig. 2 is a plan View of theunder-surface of the pressure plate;

35- Fig. 3 is a diagrammatic view of the flexing apparatus showing itsapplication to the edges of discs;

Fig. .4. is a diagrammatic view of the flexing apparatus similar to thatshown in Fig. 3. but

using a conical type of roller;

Fig. 5 is a 'perspective view of an abrasive disc supported on asupporting disc showing radial slits and flexedV edges;

45 Fig. 6 is a diagrammatic microscopic view o f apiece of iiexed fabricshowing the form of breaks; Y

Fig. 7' illustrates a modification of the method illustrated by Fig. 1in which cylindrical supporting surfaces are used to mount theabrasivecoated fabric and the compression balls respectively;

Fig. 8 is a section on the line VIII-VIII of Fig. 7:

Fig. 9 illustrates the character of the breaks madefby the apparatus ofFig. 'I when both rolls are driven at the same speed; and

Fig. 10 illustrates the character ofthe breaks made by the apparatus ofFig. '1 when the two rolls are driven at different rates of speed.

Referring to Fig. 1, a pressure plate 2, preferably of steel or similarmaterial, is secured to a rigid plate 1 by means of adjustment screws'3. Within the pressure plate 2 are mounted, by means of a race 4, ballswhich may be of steel or similar material. These balls 5 are positionedand held in place in the same fashion as it is customary to mount ballbearings, and may be of any size, the size of the balls governing thenumber of breaks or cracks made in the fabric, and thus also governingthe flexibility of the fabric produced. Should it be desired to procurea fabric with the highest possible degree of flexibility, Small ballsare used in the pressure plate since they create the largest area ofcracks or breaks which will cross and recross one another, due to thefact that the areas of the breaks made by each ball intermingle with,

or overlap, each other. 'I'his overlapping oLareas with theconsequential crossing of the breaks insures a very fine network ofbreaks and cracks, as shown in Fig. 6, which renders the fabricexceptionally ilexible.

0n the other hand, if a fabric is desired which has but a small degreeof flexibility, large balls are used. It will be apparent that, due totheir slight curvature, such large balls do not cause as sharp an angleof depression as the small balls and thus do not make as numerous breaksin the coating of the fabric; furthermore, due to this fact and to thefact that obviously a smaller number of large balls may be mounted inthe pressure plate, the lines of greatest intensity of the breaks arenot as close, nor do the areas of the breaks so made overlap to anyappreciable extent in order to bring about the fine network of breaksproduced by the small balls.

However, it is not to be understood that in using the large balls, areasare left which remain unexed since, in the performance of my method, Imount the balls in the pressure plate in staggered relation in orderthat portions remaining unexed after its passage beneath the first ballwill be treated by the next succeeding ball. One such arrangement ofthese balls is shown in Fig. 2 but, of course, it is to be understoodthat the arrangement depends on the size of the balls used and thedesired proximity of the breaks to each other, as well as on the widthof the fabric to be flexed; moreover, the size ci the ball to be used isgoverned by the size of the grit of the abrasive fabric since a goodgrade of nenibility could not be obtained upon a coarse grit iabric bythe openation of small balls thereon. In the iatter case the small ballswould press above individual grain particles, thus 'preventing ballpressure on the adhesive between them, ln. performing my invention, thecoated abrasive fabric is conducted to the iiexing apparatus where theuncoated surface is passed next to the pressure plate 2 and the entireabrasive strip travels between the balls 5 and a continuous rub ber beit6 which acts as a pad for the coated surface of the abrasive fabric.This belt 6 moves around rolls 9 and iii at a speed substantially equalto the speed at which the abrasive f abnc is caused to travel. Thesynchronized movenient of both the belt 6 and the abrasive fabricprevents any undue cutting or tearing of the rubber belt by the abrasivegrains, which would otherwise be the case should the abrasive fabrictravel at a faster rate than the belt, or the belt remain stationaryduring the forward movement of the abrasive fabric.

As the abrasive-coated fabric passes between the ball 5 of row A and therubber belt 6, the force are treated by the balls 5 in the next rows B,C

and D.

The yielding of the rubber belt 6 beneath the abrasive-coated fabrictends to allow the balls to oiler a greater strain upon the fabric andthus permits a larger area of breaks than would be possible with a beltor pad having no elastic properties; however, to give the rubber beltsome resistance, a steel plate 8 is provided beneathk the under-surfaceof the rubber belt 8.

Means, other than the pressure plate 2 and rubber belt 6, may be used aseifectively and eniciently in this method of exing abrasive fabric, suchas using a steel roll containing steel balls mounted in the staggeredrelation indicated as in Fig. 7, and a companion roll of rubber. Thepaper to be exed is passed between the steel roll and the rubber roll,the abrasive side of the fabric coming in contact with the upper sideofthe rub- .ber roll, and the balls mounted in the steel roll acting uponthe uncoated surface of the fabric, to flex'it, substantially asdescribed.

Using this means of iiexing, the degree of exibility, which is governedby the increase or decrease in breaks, may be controlled by therespective speeds of both rolls. Should both rolls travel atsubstantially the same speeds, distinct areas of breaks would occur (seeFig. 9) whichl would tend to give' a small number of breaks with littleoverlapping. ,On the other hand, if the roll acting as the rubber pad(upon which the fabric is supported) is driven Aat a faster or slowerrate of speed than the pressure roll, there will be an increase in thenumber of breaks inasmuch as the fabric will be able to receive therepeated pressure of the balls mounted in the pressure roll asillustrated in Fig. 10. In Fig. 9 the breaks are of the character madeby the balls when each ball presses 'the back of the abrasive sheet fora weaves very short time. .In Fig. 10 the breaks are of the charactermade by the balls when they roll over the back of the abrasive sheet foran appreciable period of time. The use of small rollers in place oiballs in the steel roll or pressure plate is still another means foraccomplishing essentially the Ae result.

Using the principle of my improved process in substantially the samemanner, the edges of abrasive coated discsmay be exed so as to give thema greater degree of ilexibility and better adaptation ier the varioususes to which they are put. The rubber pad or belt 6' is in thisinstance circular and is positioned upon a circular plate 8 which issupported by any suitable revolving standard 12, as shown in Fig. 3. Thepressure member 2 with the desired number of balls mounted thereon isattached to a stationary lever i3 which is held under pressure to. exertthe necessary force of the balls upon the uncoated side v of theabrasive paper. It is to be understood that a stationary standard and arevolving pressure member may be substituted, if desired.

The pressure member (using the apparatus of Fig. 3) may be so positionedwith relation to the edge of the disc that the flexing will occur eitherfrom a given concentric circle to the edge. or from a given concentriccircle to-a larger concentric circle but not to the edge. TheA latteriiexing is most advantageous since it permits the edges of the disc tobe bent under without the usual danger of breaking, and yet does notdetract from the necessary and desired stiifness of the edges. It willbe apparent that discs flexed in this manner are particularly adapted tobe attached to a supporting disc and, as such, are of greater value thanordinary discs.

Furthermore, should it be desired to flex the disc so that the edges maybe bent under and at the .same time be ileidble, it is proposed to rstflex the disc, through the use of apparatus mentioned immediately above(see Fig. 3), from a given concentric circle but not to the edge; then,in order to make the edges circumferentiallv ilexible, a cone (see Fig.4) is substituted for the pressure member containing the balls. 'Ihecone remains in a stationary position while the abrasive disc isrevolved, by means of the standard, beneath the cone in a. circularpath, and it gives to the fabric horizontal flexed lines (adjacent thecircumference and concentric therewithl which are superimposed upon thefirst mentioned lines.

Inorder that these flexed discs may be more easily bent over the edgesof any supporting disc and may present, in addition, a neat appearancecut-out portions, along the edges of these discs will greatly enhancethe commercial vvalue of my product, sincesuch slits complement and addto the'i-lexibility of the edges produced according to this invention.

die stamping by.v

' when attached thereto, I have provided radial slits various otheradditions and modifications may be made with relation to myhereindescribed method but it is to be understood that' they will bewithin the scope of my invention asdescribed in the appended claims.

I claim:

1. As a new article of manufacture, an abrasive-coated disc havingradial slits disposed equidistantly about the edge of the disc, havinglines of breakage at random directions starting from a continuous seriesof points distributed alongan annular portion of the coated abrasivewhich portion is concentric to the periphery of said disc, and havinguniformly distributed lines of breakage superimposed upon said rstmentioned breaks.

2. An' abrasive disk of approximately circular form having a stiffcentral portion surrounded by an annular portion in which the binder isbroken in short cracks extending from a series of points which lieequidistant from the center of the disk and adjacent its edge.

3. The abrasive disk described in claim 2 in which an annular portionadjacent the edge of the disk is also exed along lines radial to thecenter of the disk.

4. The abrasive disk described in claim 2 in which an armular portionadjacent the edge of the disk is slit along radial lines.

5. An abrasive sheet of approximately circular form having a relativelystiff central portion and a more flexible annular portion adjacent tothe outer circumference of the sheet, said annular portion of theabrasive article being flexible by virtue of the binder being broken inrandom directions.

6. An abrasive sheet of approximately circular form having a relativelystiff central portion and a more flexible annular portion adjacent tothe outer circumference of the sheet, said annular portion of theabrasive article being flexible by virtue of the binder being broken inrandom directions and also in directions radial to the circular sheet.

GEORGE H. DAVIS.

